The eighth commandment forbids false witness; and under this heading all the wrong that we may do to our neighbor by abusing the faculty of speech.

The sins contrary to this commandment are:

false testimony;

lying and hypocrisy;

backbiting and calumny;

evil reports;

injurious speaking;

violation of secrecy; and

rash judgments / unjust suspicions, which are like injurious words spoken in the heart.

(1) False testimony is a deposition made contrary to truth, and upon oath, in a court of justice. False testimony is a mortal sin, for it includes perjury, which does not admit lightness of matter.

(2) To tell a lie is to speak against one's conviction, to say what one believes to be false knowingly, and with the intention to deceive. There are three kinds of lies, namely:

The "jocose" lie; which is told for the sake of merriment;

The "officious" lie, which is told to excuse or to spare oneself or others some inconvenience; and

The "pernicious" lie, told in order to injure one's neighbor.

There is NO lie in words said in jest, the untruth of which is apparent; or in certain phrases which appear false, though their meaning is readily understood. A real lie is a sin, generally venial; but it becomes mortal when it causes a serious injury to the honor or goods of one's neighbor.

Hypocrisy is also a kind of lie. It consists in borrowing the appearance of virtue in order to gain the esteem of men.

(3) Backbiting is the injury done to the reputation of our neighbor, by unjustly revealing his hidden faults and defects.

Calumny consists in imputing to our neighbor a crime which he has not committed, or in exaggerating a real fault.

To constitute backbiting, what we reveal must NOT have been public before, and it must be unjust to reveal it; because Christian charity sometimes requires us to make known our neighbor's faults in order that he may be corrected, or hindered from perverting others, or in order to prevent some evil.

In such cases the faults should only be made known to those who ought to be acquainted with them, such as parents, masters, and superiors. It is NOT backbiting to give disadvantageous, though correct, information concerning another, when we are consulted by persons interested in ascertaining it, when there is question of some projected alliance, or some other affair of importance.

Backbiting and Calumny are called detraction. We may be guilty of detraction in several ways, namely:

by attributing to our neighbor a fault which he has not committed, or a defect which he has not;

by exaggerating his faults;

by proclaiming as certain those which are uncertain;

by making known those which before were hidden;

by insinuating them;

by causing suspicion by speeches such as the following: "It is reported, They say";

by putting an unfavorable interpretation on the good actions of our neighbor;

by denying his good qualities and seeking to diminish his merit; sometimes by praising him coldly, or by keeping silent when such silence is an approval of the evil which others are retailing, or a disavowal of the good which is spoken of our neighbor.

Detraction and defamation are not only committed by the tongue, but they may be committed in a still more disastrous way by the press, in newspapers and other publications.

It is no more allowed to defame a religious order, or any kind of community, than any individual person. Slander and Calumny, all other things equal, are even more serious in the former than the latter case.

It is forbidden also to defame the dead, both because their memory should be respected, and also because by defaming them their parents and relations may be seriously injured.

It is never allowed to participate in detraction, or to listen to it with pleasure. We must, if possible, excuse our neighbor; or, if we have the authority to do so, we must impose silence on the detractors; if not, we must show by our own silence or serious looks that we disapprove of such conversation; or, according to circumstances, we should turn it adroitly to some other subject.

When by slander or calumny we have injured our neighbor in his reputation or possessions, we are bound to repair the wrong as far as possible, either by retracting the calumny or by speaking well of the person whom we have defamed by our slander.

(4) Evil report, which is called by theologians "susurration", consists in repeating to another the unfavorable things we have heard concerning him from a third person. This detestable failing has the effect of sowing discord where peace reigned before, and of disturbing the good relations existing in families and between friends. It is a graver sin than the sin of detraction.

(5) Injurious words are offensive words spoken to our neighbor to his face; they may constitute a contempt and an affront which wound his honor. We are guilty of this sin by using hard words, reproaches, by speaking in insinuations, and by cutting raillery. There is, however, NO sin in a simple joke amongst friends by way of recreation, unless we foresee that the object of it will be annoyed.

He who has done an injury to another must make reparation as soon as possible.

(6) We sin also by the abuse of the tongue when, without sufficient cause, we reveal a secret that has been confided to us. The following are cases where we are dispensed from keeping a secret:

when it has become notorious and public, for then it is no longer a secret;

when the revelation of the secret is judged necessary for the public good, or for some other very serious reason.

We of course are speaking of natural secrecy, and NOT the sacramental secrecy of confession, from which nothing, under any circumstances, can dispense, and which is guarded by the seal of God Himself.

The Law of Secrecy not only forbids us to betray what has been confided to us; it also forbids us to extract the secrets of others; and in that is comprehended the breaking of the seal of letters that are not addressed to us, unless we act by legitimate authority, or for a sufficient reason. In this, as in all else that regards the law of justice and of charity, we must act on the grand principle of doing to others as we should reasonably wish they should do unto us.

(7) To judge rashly is to judge badly of another's actions without just cause.

When doubts or suspicions or derogatory judgments concerning our neighbor occur to our minds, we must NOT dwell on them, but rather disapprove and reject them as soon as ever we perceive them to be rash and unjust.

The doubts and suspicions of superiors, of masters, and of fathers of families are NOT unjust or blameworthy, for it is their duty to watch over their inferiors, and, to a certain degree, mistrust them, that so they may prevent them from doing wrong. They act in such cases from motives of prudence. We may consider the doubts which we form in order to avoid some harm, or to take precautions against the possible occurrence of evil that might happen, of a similar description.

In order to observe the eighth commandment well we should purify our hearts from all jealousy, envy, and hate, and ask God's help to enable us to govern our tongues, saying with the prophet:

"Set a watch, O Lord, before my mouth, and a door round about my lips. Incline not my heart to evil words, to make excuses in sins." - Psalms 140:3-4 (Douay-Rheims)